Steam reheater



June 30, 1953 J. H. STELLING STEAM REHEATER 6 Sheets-Sheet l Filed Feb. 18, 1949 J. H. STELLING STEAM REHEATER June 3o, 1953 6 Sheets-Sheet 2 Filed Feb. 18 1949 TIl lll: l

J. H. STELLING STEAM REHEATER June 30, 1953 6 Sheets-Sheet 3 y Filed Feb. 18, 1949 June 30, 1953 J. H. STELLING STEAM REHEATER 6 Sheets-Sheet 4 Filed Feb. 18, 1949 .Hume 30, i953 J. H. STELLING STEAM REHEATER 6 Sheets-Sheet 5 Filed Feb. 18, 1949 J. H. STELLING 'STEAM REHEATER June 30, 1953 6 Sheets-'Sheet 6 Filed Feb. 18, 1949 Patented June 30, 1953 UNITED STEAM REHEATER John Henry Stelling, Quincy, Mass., assignor to Bethlehem Steel Co Pennsylvania mpany, a corporation of Application February 18, 1949, serial No. 77,257

4 Claims. l

My invention relates in general, to a heat exchanger, and more particularly to a turbine steam reheater adapted for marine use.

rBhe steam reheater is a heat exchanger of the shell and tube type designed to receive the exhaust from a steam turbine in a saturated or wet condition and to dry out and superheat this exhaust at substantially constant pressure before passing it on to the inlet of the next turbine in the set. In the modern high pressure, high temperature reheat cycle type ofA marine propulsion installation, three turbines. and two reheaters vare often employed. The reheater located between the high and intermediate pressure turbines is designated as the high pressure reheater and that between the intermediateand low pressure turbines. as the low pressure re heater. The turbine Steam to, be reheated flows across and outside ofv a bank ofsteely tubes ywhich are heated by superheated steam: at boiler pressure.

in a typical marine, installation ofv this. type the high pressure reheater receives steam at approximately 191 p. s. i. g, pressure and 384?. temperaturev with 2.5% moisture from. the eX- haust of the high pressure turbine and heats it to 565 F. temperature before passing. it to the intermediate pressure turbine. The low pressure reheater receives steam at about l'7`p. s. i. g. pressure and 254 F; with 0.5% moisture and heats it to 565 F. temperature before passingit to the low pressure turbine. Both reheaters receive heating stem from the main boiler super-v heater outlet; at l500-p. s. i. rg; pressure andY 750" F. temperature.

Except for its somewhatlarger size,v the:v low pressure reheater will generally be similar to the high pressure unit, so that a; description of the former will suffice forboth.. The conventional` reheaters have been `of the shell and tube type, with one pass ofA U-tubes expanded into a heavy steel tube sheetv forged integrallyY withY the steam chest. Characteristic'features, therefore, have. been the Very thiclrtubel sheet (necessitated by the very high steamV pressure), the;

close spacing of the. tubes'andf correspondingly thin ligaments in the tubeY sheet, andf the type oi head joint which consists of a exible; diaphragm sealed by a gasket bolted tcfthe steam chest andbacked up byl aA very thick coverplate.-

In marine service, this type of' construction has developed two major-faults. The-highpres'- sure joint between the steam chest and the-cover deal of trouble from leakage. Severalfmodica tions ci jointV designs and gasket; types` havebeen tried, with only pfrtials success', andi seal Welding the joint vmakes.accessztoathe tubesheetf for rep airs extremely; diicult.

tion and industrial practice, with. apparently good results. Differences between. marine and. stationary operating. conditions, such as the drainage and temperature uctuations during maneuvering and in the more. frequent. Warm-up. and shut-down cycles of a marine plant, are undoubtedly responsible.

One object of my invention,y therefore, is to provide an arrangement of Welded. tubes,Y elements, element headers, element header manifolds and supply and drain headers in such a Way as to form the equivalent. of a standard staggered pitch tube bundle without. the tube sheet and high pressure steam. chest cover jointA associated with the usual. reheater design.

Another object is an arrangement of. the. ele-- ment tube supporting plates. inV such a Way that when the individual' elements are assembled to form a complete. tube bundle the. element. sup:- porting plates align themselvesv to form a desired barile pattern for directingf the steamto be heat.- ed back and forth across the tube bank in the most eflicient manner.

A further object is av construction. permitting, ready removal of any tube elementwithout. disturbingv the' remaining elements.

Still another: object is an arrangement of the element headers with their axes. parallel to the. axes of the tubes which they. serve..

Other objects, purposes and advantages of my' invention will appear hereinafter inthe. spe'cication and in the appended claims.

In order to render my invention more. clearly understood, I shall now refer to the attached six' (6) sheets of drawings forminga part of this specification and' in which like characters. of A Fig. 4 is a top planview'with' theshell partly' broken'avvay to show the interior' arrangement;` Fig. 5 is a transverselvertical section on` the.

line-5 5 of Fig; 3;

Fig. 5 is ay transverse vertical section also on the line '-ofFig. 3, but with the tube elements omitted j Fig. 7l is a transverse vertical section on thev line l-l' of. Fig. 2, with l tubessimilarly f omitted; Fig. 8 is a transverselverticallsection on'tlre line` 3--8 of Fig: 2; also with' tubesfomitted;

Fig; 9-2is .a verticalsectionfofa chill ringsuch` as is used in welding the heating steam drain;

Fig. 10 is a detail vertical section of the heating steam drain;

Fig. 11 is a transverse horizontal section on the line ll-l i of Fig. 16, and showing the assembly of a tube support plate with tubes and retaining plate;

Figs. 12 to 16 inclusive are additional detail views of the tube support assembly;

Fig. 17 is a horizontal section of the inlet header manifold;

Fig. 18 is a fragmentary vertical section on the line l8-i8 of Fig. 17;

Fig. 19 is a vertical transverse section on the line ls--IQ of Fig. 17;

Fig. 20 is a longitudinal vertical detail section of the terminal end of an inlet element header;

Fig. 2l is a vertical section on the line 2l- 2l of Fig. 20; and

Fig. 22 is a Vertical transverse section on the line 22-22 of Fig. 20.

Referring now more particularly to Figs. 1 to 4 of the drawings, the elongated steel shell l of my reheater preferably comprises two cylindrical sections, a forward or header section 2 and a rear or tube-enclosing section 3, the former section being slightly larger circumferentially and having an outlet connection d therefor and the latter section being flared outwardly as at to correspond and havingr an inlet connection E for steam from the turbine. The ends of the shell are closed by the dished heads l and 8, the rear head l being permanently secured in place by welding or the like. Suitable means such as standard hex nuts e on studs lll and bolts H, compressing standard metallic-asbestos or lexitallic type gaskets l2, between the pairs of annular flangesV i3 and Hi, removably secure the shell portions and the front head 8 together in axially assembled relation. Welded support brackets i5 and lifting lugs are also provided in conventional manner.

The inlet nozzle il passes the high pressure (1509 p. s. i. g.) heating steam through the disc plate i8 mounted by means of the ring plate i9 on the top of the shell and within the shell is connected by means of the 90 L 2a, pipe 2l, reducer fitting 22, 45 L. 23, and T 24 to the transversely arranged horizontal steam supply header pipes 25. Weldedinto said header pipes 25 are end pieces 2S and apair of inlet element header manifolds 2l, which are for-gings specially man chined and provided with drilled passages 28 and sockets 253 as shown in Figs. 17, 18 and 19 to distribute the heating steam to fifteen longitudinally arranged horizontal inlet element headers 38. Said inlet element headers 30 are welded into the sockets 2t ci' the element header manifolds by means of standard socket welding procedure.

Each of the fifteen aforementioned inlet element headers @il (the bifurcated outer end piece 3l of one of which is shown in Figs. 20 to 22 inclusive) in turn distributes steam through drilled channels 32, 33 and 34 to the inlet legs 35 of twenty-three tubes 36, which are similarly welded into the sockets 3l of the element headers 3D by means of socket welds. Said tubes 3E are of U-shape with vertically disposed inlet legs 35 as aforesaid and outlet legs 38 (see Fig. 1) alter--Y nately offset to permit arrangement in staggered pairs and with progressively enlarged radii of end curvature to permit their nesting together in an intertting relationship.

The outlet legs 3s of said tubes 36 are connected in the same manner to a parallel assembly 4 of fteen horizontal outlet element headers 39, transversely disposed outlet element header manifolds t5, drain header pipe lll, drain header T 42, 45 L 13, pipe 54, 90 elbow t5, and a heating steam drain connection it on `disc plate 41 mounted on ring f3.8. A small vent i9 is provided on the drain connection to vent air and noncondensable gases from the system, also a gage glass connection Sil and flange 5I, as shown in Fig. 1D. Welding is facilitated by removable chill rings '52 (Fig. 9).

A unit consisting of the two element headers 3Q and 39 and twenty-three heating tubes 36 is called, for purposes of designation, an element. The tubes of each element have attached to them tube support plates 55 (Fig. 13) having outward slots 5s which serve to support the tubes and maintain them in the desired relationship to each other. 'She tubes' are retained in these support plate slots 5s by correspondingly inwardly slotted side retaining strips 55 (Figs. 1l, l2, i5 and 15) and welded stop strips 5G (Figs. le and 16).

It will be observed that the tubes of each element are arranged in such a way Vthat when all the elements are assembled, a cross-section of the tube bundle (Fig. 5) finds the tubes in a conventional close staggered pattern, which serves to promote heat transmission and ccnserve space.

The tube support plates 53 of a number of adjacent elements are welded together in groups at top (see Fig. 12)` and bottom, preferably with a very slight open space left between them, to form in effect vertical transverse baffles. As shown in Fig. 3, the location of these groups of plates on the elements is such that when the elements are assembled into a complete tube bundle the aligned support plates 53 form a tortuous baie system directing the flow of turbine steam transversely back and forth across the tubes for 'maximum contact and most efrlcient transmission of heat.

In order to confine the turbine steam to the path across the tube bundle, thereby increasing its velocity and preventing longitudinal bypassing of the tubes, the segments of the shell above and below the tube bundle are closed on` by the upper and lower horizontal bailie plates 5'? and 58, welded to longitudinally disposed fiat bars 59 and stiffeners 60, and to transverse kangle bars 6I, and which run parallel practically the entire length of the rear section 3 of the shell.

iTransverse short upper and lower vertical end pieces S2, 63, ed and 65 prevent steam from flowing through the void spaces and thus bypassing the tubes. An impingement baille S6 in way of the turbine steam inlet prevents erosion of the tubes by the wet steam entering the unit, and there is also a smaller impingement baille 6'! for low pressure turbine drain connection 68.

Horizontally and vertically disposed flat guide bars 69 and '10, at the sides ofthe tube bundle, and strengthened by horizontal and vertical stiifeners ll and '12, assist in maintaining tube alignment between the top and bottom barile plates. At the header end, support brackets l, transverse horizontal lower and upper flat bars 14 and i5, and an upper baffle plate 'i6 are welded as shown in Fig. 5 to support the initial group of tube support plates 53. There are also provided end plate Tl with removable cover plate 7B, and side half-baille plates 'I9 braced by flat bars 89 and additional stiffeners 8l.

Underv operating conditions, the above delscribed arrangement of element headers with their axes parallel to rather than perpendicular to the axes of the tubes is ideally suited to reheater service, since the quantity of steam required by the tubes is governed by the amount of heat that can be transferred from them to the surrounding turbine steam, which, owing to the low heat transfer coefficient obtaining for this condition, is small and can readily be handled by headers of this type without appreciable pressure drop or requiring excessive initial velocity.

The welded header type reheater completely eliminates both the large diameter high pressure steam chest cover joint as lwell as the tube sheet with its troublesome rolled-in tube joints. Welding of the tubes into the element headers and of the element headers into the element header manifolds is accomplished by means of standard socket welding procedure, of a type that has been in successful use for a long time in connection with main steam piping. This type of welding is permitted by marine classification and inspection authorities without radiographic examination, a factor which greatly facilitates construction.

A further advantage of this unit is its ready accessibility for inspection and repair. The shell can be opened at two places for inspection of the high pressure parts. Isolation of a defective element can be readily accomplished by removing the shell end head, cutting or burning out a section of the element headers of the defective element and welding plugs into the stubs remaining in the element header manifolds. This will permit the unit to .be returned quickly to service. Replacement of the defective element can then be postponed until some convenient time such as in connection with the annual inspection and overhaul of the vessel.

Although I have described and illustrated my invention in considerable detail, I do not wish to be limited to the exact and specific details thereof as shown and described, but I may also use such modifications, substitutions or equivalents thereof as are embraced within the scope of the invention or as are pointed out in the appended claims.

I claim:

1. In a heat exchanger, the combination of a substantially horizontal cylindrical container provided with inlet `and outlet connections for the medium to be heated at opposite ends of the container and with vertically spaced inlet and outlet connections for the heating medium at the same end of the container las the heated medium outlet, a pair of substantially horizontal manifolds disposed in parallel relation crosswse of the container and connecting to the heating medium inlet and outlet connections respectively, a plurality `of longitudinally disposed parallel element headers connected at right angles to said manifolds, and a plurality of horizontally arranged staggered U-shaped tubes having alternately offset vertical legs interconnecting vertically aligned pairs of element headers.

2. In a heat exchanger, the combination of a container provided with an inlet connection for the medium to be heated at one' end of the container, an outlet connection for the heated medium and an adjacent inlet connection for the heating medium at the other end of the container, an outlet connection for the heating medium in vertically spaced relation to the inlet therefor, a plurality of U-tubes connected to the inlet and outlet connections for the heating medium and forming a horizontally staggered tube bundle, tube support plates having outwardly opening slots in alternately staggered relation on opposite side edges, tube retaining U-shaped strips having corresponding inward slots and engaging said plate side edges, and stops welded onto the tubes at opposite faces of the tube support plates, a plurality of assembled tube support plates and retainer strips being Welded together and arranged t0 cause the medium to be heated to pass transversely back and forth through said staggered tube bundle.

3. In a steam reheater, the combination of a horizontal container, an inlet connection for high pressure reheating steam at the top of the container near one end thereof, an outlet connection for said reheating steam located thereunder at the bottom of the container, an inlet connection for the steam to be reheated near the opposite end of the container, an outlet connection 4for the reheated steam adjacent the reheating steam inlet, a plurality of U-tube elements connected 'between the inlet and outlet connections for the reheating steam, and recessed vertical plates and cooperating recessed closure members for retaining the U-tube elements in assembled staggered relation, sai-d plates being aligned to coact with the staggered U-tube elements to provide a. tortuous baffle system for thesteam lbeing reheated.

4. In a Isteam reheater for marine use, the combination of a horizontal shell divided into two section-s removably secured together, an inlet connection for the steam to be reheated in the upper part of one end of the shell, an outlet connection for the reheated steam in the -upper part of the opposite end of the shell, an inlet connection lfor reheating steam adjacent the reheated steam outlet, an outlet connection .for said reheating steam in the bottom part of the shell vertically beneath the reheating steam inlet, a plurality of unitary U-tube elements including inlet and outlet manifolds connected to the inlet and outlet connections for the reheating steam and comprising a horizontal tube bundle, tube support means providing a serpentine path for the steam to be reheated across the tube bundle, horizontal plates above and below the tube bundle to confine the steam to be reheated to the desired path, and an impingement baiile interposed between the inlet connection for the steam to be reheated and the tube bundle.

. JOHN HENRY STELLING.

References Cited in the file of this 'patent A UNITED STATES PATENTS Number Name Date 1,592,538 Price July 13, 1926 1,883,605 Davy Oct. 18, 1932 1,884,778 Lucke Oct. 25, 1932 1,919,029 L11-cke July 18, 1933 1,929,376 Trainer et al Oct. 3, 1933 1,962,362 Reed June 12, 1934 2,038,002 Ris Apr. 21, 1936 2,143,157 Kotzebue June 13, 1936 2,183,160 Coulter et al Jan. 19, 1938 2,256,882 `Seb'ald Mar. 11, 19.39 2,268,507 Gertzon Dec. 30, 1940 2,269,619 Carpenter Jan. 13, 1942 2,432,362 Worn et al. Aug. 1, 1942 FOREIGN PATENTS Number Country Date 501,855 Germany June 19, 1930 

